A fuel filter of a fuel system of an internal combustion engine is used to remove contaminates from the flow of fuel, thereby avoiding the transmission of the contaminates to, for example, the high pressure fuel pump or the injectors of the fuel system. Unfiltered fuel can contain particulate contaminates, such as dirt or rust, or fluidic contaminates, such as moisture from the fuel tank of the fuel system. The transmission of such contaminates may result in increased wear rates for the components of the fuel system and a less efficient fuel burn.
A typical filter assembly comprises a filter head including ports that connect the filter assembly to the fuel system, and a filter can secured to the filter head. The filter can contain a filter medium. The filter medium forms part of a filter cartridge located within the filter can. Optionally, the filter assembly can also include a water storage capacity or decantation volume for storing the fluidic contaminates once they have been filtered out of the fuel flow.
Filter servicing is necessary either when the filter medium becomes obstructed by the accumulation of the particulate contaminates and needs to be replaced, and/or when the water storage capacity is full. When servicing the filter medium, either the filter cartridge alone is replaced or the entire filter assembly. The former type of filter is known as a ‘removable cartridge filter’, and the latter is known as a ‘throw-away filter’.
The cost of replacement parts of a removable cartridge filter is lower when compared to a throw-away filter because only the removable filter cartridge is replaced. However, a throw-away filter benefits from lower service labour cost due to the ease with which it is replaced.
Furthermore, when servicing a removable cartridge filter, unless means are provided to protect the clean side of the filter medium, the filter medium will be subject to the possibility of contamination. For example, if a removable filter is constructed so that fuel flows across the filter medium in a radially outwards direction from an inner dirty side to an outer clean side of the filter medium, the clean side of the filter medium will be exposed to the possibility of contamination when being handled during servicing. Conversely, if the fuel flows across the filter medium in a radially inwards direction from an outer dirty side to an inner clean side of the filter medium, the clean side of the filter medium will be subject to the possibility of contamination if the cartridge is handled at upper and lower ends of the filter medium. In both of these configurations, unless measures are taking to protect the clean side of the filter medium, the clean side's proximity to an outlet of the removable cartridge filer will also expose it to possible contamination.
Whereas, as a throw-away filter is supplied “ready-to-fit”, the filter cartridge itself is not handled during maintenance and, therefore, is not subject to the possibility of contamination.
A further issue with some conventional filter assemblies relates to the use of a heater, the heater being arranged to heat the fuel to prevent the formation of wax particles in the fuel prior to filtration, for example. The heat transfer capacity of the heater of a conventional filter assembly is limited by its relatively small heat exchange surface area. In addition, typically the heater is fixed on the periphery of the filter assembly which increases the overall size of the filter assembly and impacts on the limited space available in the engine compartment.
A further issue with conventional filter assemblies relates to the proximity of the fuel flow to the fluidic contaminates in the decantation volume. For example, if the fuel flows into a heater at the top of the filter assembly and exits the heater into a decantation volume at the bottom of the filter assembly, the fluidic contaminates in the decantation volume become disturbed and entrained into the fuel flow.
It would be desirable to provide a fuel filter that overcomes or at least alleviates at least one of the above-mentioned problems and disadvantages in the prior art.